Circuit breaker



Dec. 8, 1942. G, A; HEAUS 2,304,253

CIRCUIT BREAKER Filed March 6, 1940 3 Sheets-Sheet l /C g4, a ijf/Wu,

M ATTORNEY Dec. s, 1942. G. A. Hams 2,304,253

C IRCUIT BREAKER l NVENTO 650/2616 Aff/u /s ATTORNEY Dec. 8, 1942. G. A.HEADS CIRCUIT BREAKER Filed March 6,- 1940 3 Sheets-Sheet 3 l kBYPatented Dec. 8, 1942 2,304,253 CIRCUIT BREAKER George A. Healis, Aidan,Pa., assignor, by mesne assignments, to The Pennsylvania Company forInsurances on Lives and Granting Annuities, Philadelphia, Pa., acorporation of Pennsylvania Application March 6, 1940, Serial No.322,444

(Cl. 20D-106) 6 Claims.

This invention relates particularly to air circuit breakers for use inindustrial applications and for use on switchboards for the control ofcircuits.

The main object is to provide a breaker of this type of compact form,occupying comparatively small space and having a relatively high ampereinterrupting capacity. It is adapted for use on circuits having voltagesup to 600 or more and for normal currents of several hundred amperes,the interrupting capacity on overloads being far higher. Another objectis to provide a separate enclosing apartment of improved form for eachpole cf the breaker which may be assembled and disassembled readily andconveniently. Another object is to relate the contact parts in such amanner as to insure a firm and adequate engagement and to provideauxiliary contacts and associated means which will effectively withstandand reduce the arcing. Another object to is provide a related overloadcontrolling means of improved form which will serve to impose a timedelay of proper amount in its control under moderate overloads whileserving to secure instantaneous opening of the breaker upon the occur-Other oband at right-angles to the shaft of the contact l arms showingthe breaker closed; Fig. 3 is a vertical section through the mechanismcompartment at right-angles to the shaft of the contact arms showing theparts when the breaker is closed; Fig. 4 is a similar view showing theparts when the breaker has been tripped; Fig. 5 is a similar viewshowing the parts in position for reclosing the breaker; Fig. 6 is aVertical longitudinal section of one of the overload devices; and Fig. 7is a view similar to Fig. 6 showing a modified form.

The breaker is shown mounted upon a rear insulating panel l and isenclosed by a metal casing 2 which surrounds the two sides, front andbottom of the breaker and has inwardly turned edges 2a at the top of thesides and an inwardly turned edge 2b at the top of the front, whichedges embrace the top portion of the breaker. At each lower side of thebreaker and within the casing is mounted a sheet metal support 3, the Irear portions ci these two supports being bent inwardly and secured tothe back ofthe panel by bolts 3a. These supports form the bearings forthe main shaft 4 of the breaker. This shaft is of square cross-section,as shown in Figs. 2 to 5, the ends of the shaft being round and beingjournaled in the supports 3. The square portion of the shaft isenveloped by insulating material 5 oi suitable thickness and carriesinsulating shields or disks 5a which extend outwardly beyond theinsulation on the shaft. In the particular form shown, the breaker is athree-pole breaker having three sets of contacts adapted for use in athree-phase circuit. A contact arm 6 is provided for each phase and isxed to the main shaft at its lower end by being clamped thereto, asshown in Fig. 2. These movable contact arms shown are generally ofT-angle form for strength having their faces toward the rear forengagement with fixed contacts and are composed of a material of highconductivity, such as forged copper. Intead of these arms beingconnected in circuit by the usual flexible conductor, they cooperatewith contacts which are connected to the incoming and outgoing leadswhich avoids the necessity of connecting flexible leads to the contactarms.

Fig. 2 shows the form of the iixed contacts with which the arms 6respectively cooperate, the parts being shown in closed circuitrelationship. The xed contacts are each of similar form and include alower Contact which remains in engagement with the arm 6 at all times,an upper main contact and an arcing contact above the main contacts.Considering iirst the lower main contact, this is in the form of arecessed or cupshaped copper block 'l having side plates 'Ia and forms abearing with an open top portion. Pivotally mounted in this bearing is apair of contact fingers B of copper, the end surfaces of these lingershaving a bearing against the walls of the recess for securing a goodconductive engagement. A pin lla mounted in the side plates 'la servesto retain the fingers in the recess, there being suilicient freedom ofmovement on the pin to permit the edge surfaces of the fingers to alwaysmaintain contact with the walls of the recess. 'I'he contact block ismounted on the panel I by a screw bolt 'lby which extends through fromthe back of the panel into the block. A stii spring S is introducedbetween the rear of the lingers 8 and an upwardly extending portion ofthe block l, an insulating disk 9h being located at the rear of thespring for preventing current from passing through the spring. Thespring forces the front portions of the fingers 8 firmly against thelower face of the contact arm 6. A T-shaped piece of metal 9a is seatedin notches on the inner edges of the contact fingers, the tongue portionof the T extending within the spring and serving to hold the front endof the spring in proper position in relation to the fingers. These lowermain contact fingers are maintained in good electrical connection attheir front upper ends with the lower portion of the contact arm in allpositions thereof by the pressure of the spring, the lower ends of thefingers being forced against the walls of the block 'I in all positions.The pivotal support of the lower ends of the ngers in the block permitsthe fingers to move against the pressure of the spring when the contactarm is moved to closed position. The outside lead is connected to thebolt I which extends through the panel and is connected to a block atthe inner end of the copper conducting strip Ila. This strip continuesand is wound to form an overload coil II which is shown with its turnsspaced apart from each other and having its rear end connected to theunderside of the block 'I by a screw bolt 1c.

The upper main terminal is of the same form as the lower main terminaland is turned downwardly instead of upwardly, the parts beingcorrespondingly numbered. The outside lead is connected to the bolt IDawhich in turn is screwed into the rear of the block 'I to form a goodelectrical connection. The bolts I0 and IOa and the parts connectedthereto are held in place by nuts IUI) which are threaded on the boltsand drawn up against a spacing bushing Ic.

The upper arcing contact is located above the upper main contact and issimilar thereto, the corresponding parts being given the same referencecharacters. The faces of the fingers 8 of the arcing contact havesecured thereto a metal face plate 8b of non-oxidizing and non-weldingmaterial which will not volatilize under the effects of any electricarc. The upper inner face of each contact arm 6 is similarly faced witha sheet 6b of similar material, the face plates 6b and 8b forming anauxiliary contact engagement when the breaker is closed, as shown inFig. 2. The copper cupped-shaped block 'I of the arcing contact isextended forwardly somewhat and faced with a. plate 'Id of'non-oxidizing, nonwelding and non-volatilizing material. The upper blockI is held in place on the panel I by a screw bolt Ib which passesthrough the panel and engages the rear of the block. The contact block'I of each of the contacts is provided with a forward extension 'Iewhich limits the outward movement of the fingers of the contacts whennot engaged by the contact arm.

The fingers of the lower main contacts are directed upwardly while thoseof the upper con tacts are directed downwardly. It results that themagnetic field set up by the passage of current through the contacts andthe contact arm, tends to force the fingers outwardly against thecontact arms and thereby increases the contact pressure against thearms. This added pressure serves to improve the electrical Contact ofthe parts.

At the side of the auxiliary arcing contacts of each pole of the breakeris a magnetic blow-out coil I2 formed of a single turn of a metal copperstrip positioned in a vertical plane, as shown in dotted lines in Fig. 2and in ful1 lines in the upper right-hand sectionalized portion of Fig.1.

CIX

Each of these three strips I2 has an end I2a 75 extending to one sideand connected to the top of the upper block 'I while the other end ofeach coiled strip I2 has an extension I2b to one side which is connectedto the top of the block 1 of the upper main contact.

The open position of each contact arm 6 is shown in dotted lines in Fig.2. When the contact arm shaft 4 is turned to move the arm to its closedposition, its face plate 6b first engages the face plate 8b of thearcing contact fingers and turns them downwardly away from the faceplate Id and rearwardly towards the panel I against the pressure of thespring 9. Continued movement of the arm 6 brings it into additionalengagement with the contact fingers 8 of the upper main contact andforces them inwardly against the pressure of their spring 9. Fig. 2shows the parts in fully closed position, the cir cuit then passing fromthe lower bolt ID through the overload coil II to the lower mainterminal block 'I to its fingers 8 and then through the arm 6 to thecontact fingers 8 of the upper main terminal and then through theterminal block to the upper bolt Illa. When the contact arm 6 is movedto its open position, the contact between this arm and the fingers 8 ofthe upper main contact is interrupted first which results in the currentpassing from the upper end of the arm 6 through the contact plates 5band 8b and through the fingers 8 to the block I of the arcing contact,then by the connection I 2a through the coil I2 to the upper maincontact block I by the connection |21) and thence to the outside circuitthrough the bolt Illa. This creates a strong magnetic field across thearcing contacts. As the arm 6 continues to move outwardly the fingers 8turn on their pivot in the upper contact block under the pressure oftheir spring until they engage the outer portion of the block. The upperend of the arm 6 then breaks contact with the plate 8b drawing an arc atthe separation of the contacts. This arc is forced upwardly by themagnetic blow-out and as the arc becomes attenuated, it is forcedupwardly to extend between the contact plate 6b and the contact plate'Id where it is finally interrupted and quenched and the gases cooled bythe auxiliary means to be described.

Each pole of the breaker is separated from its adjacent pole andenclosed within molded barriers of insulating material whereby each poleis enclosed within an insulating chamber. This eliminates the danger offiash over between poles which otherwise might be caused by the flare ofionized gases during interruption. Furthermore the gases are forcedoutwardly through a quenching chamber where they are cooled beforepassing from the top of the breaker. The insulating barriers orpartitions on each side of each pole are each made up of two separateportions. One portion I 3 is of general triangular shape and forms therear lower portion of each partition. It backs against the lower portionof the panel I, being secured thereto by screws I3a, as shown in Fig. 2.The top of this portion of the partition extends forwardly from thepanel I on a horizontal line I 3b close to the contact shaft 4 and thencircles half-way around the rear lower portion of this shaft and thenextends diagonally downward as shown by the line I3c in Fig. 2 close tothe trip shaft I4, passing halfway around the lower inner side of thisshaft and then extends downwardly at the surface I3d to an insulatingplate I5 across the bottom of the breaker. This plate is secured to thelower enlarged edge I3e of the partition I3 by screws I3f. The otherportion I6 of the insulating partition engages the portion I3 alreadydescribed with an overlapping joint and butts against the upper portionof the panel I. It is secured to the panel by an upper row of screwbolts Ita and a lower row of screw bolts Ib. The corner screw bolts I6aalso pass through the enclosing metal casing 2 and serve to hold thelatter in place while the intermediate screw bolts Ia pass through afront insulating plate il within the front portion of the casing 2 andserve to hold this plate in place against the front vertical edges ofthe partition portions I5. The screw bolts iSd are tapped into a metalstrip I8 across the topl of the rear ofthe panel. The screw bolts itl)are centrally located and pass through the iront insulating plate Il andthrough the partitions i and panel I and engage nuts Iiic at the rear ofthe panel; At the lower corners of the breaker screws I 6d pass throughthe casing 2 and er1- gage inserts in the lower ends of the partitionportions I. Screws Iid between the lower corner screws pass through theplate Il and engage inserts in the lower ends of the intermediatepartition portions I 5. The barrier partitions, front insulating plateil, lower insulating plate I5 and the casing 2 thus are held lirrnly inxed position.

The rear of the portions It extends from the top of the panel I down tothe lines i3?) of the panel portions i3 and then extend forwardly andcircles around the upper and front portions of the shaft I and thenextends diagonally downward along the line ISC to the trip shaft It andcircles around the front and upper portions of this shaft to the linei3d and then engages the lower insulating plate I5. The insulating disksor shields 5o on the shaft Il are positioned to engage the sides of thetwo portions I3 and i5 where they encircle the shaft 4 for the purposeof closing the spaces around the shaft and thereby isolating the metalparts of each pole of the breaker from other poles. Similarly the tripshaft I is provided with insulating disks Ia for closing the` spacesaround this shaft where the barrier parti.- tions encircle the shaft.The top and front edges of the barrier portions it are wider than otherparts thereof, as well as the central longitudinal portion through whichthe screws Ib pass. The upper parts of the barriers l form enclosedvertical spaces ide for separately enclosing the blowout coils l2, asshown in Fig. l. On each side of the vertical spaces ie are plates If ofinsulating arcresisting material which are secured to the sides at thetop, front and mid portions of the molded insulation forming thebarriers I 5. The openings ite extend to the panel l which permit thebarriers I6 to be moved into position from the front of the breakerduring assembly envelop the blow-out coils i2, slots being provided atone side in the plates Itf at the rear to permit passing beyond theleads I2a and i222 of the coils.

On each pole of the breaker is a chute for quenching the arcs formedwhen the breaker is opened and for cooling the gases before they passfrom the breaker. These chutes are formed of side plates 23 ofinsulating material small front plates vila and rear plates 26h at thetop of the chutes where they extend above the casing of the breaker,shown in Figs. l and 2. The plates .2li are provided with projections2te on each side which extend longitudinally from front to rear andengage slots in the sides of the par- 'tions i6 abovethe plates If forretaining the chutes in position. AIn assembling the parts, the chutesare slid in from the front of the breaker and are retained in positionby the front insulating plate Il. The chutes extend downwardly at thefront of the breaker, as shown in Fig. 2, and

thus approach close to the region Where the arcsy are formed between thebreaker contacts. Between the plates 20 extend a number of pins 20d ofinsulating arc-resisting material and are positioned in staggeredrelation, as shown in Fig. 2. When the arcs are forced upwardly from thecontacts of the breaker, they strike these insulating pins which serveto quench the arcs quickly and to cool the gases as they pass upwardlyand out through the chutes.

The operating mechanism of the breaker is enclosed within a spacebetween two of the barrier partitions. It is supported by a U-shapedsheet metal frame 2I with the base of the U secured to the panel I byscrew bolts 2Ia. The two sides of the frame extend forwardly from thepanel and are provided with downwardly extending legs 2 ib. Fig. 5 showsthe position of the parts when the breaker is open and in condition tobe closed by the downward movement of the closing element or handle.Fig. 3 shows the parts when the breaker is closed and Fig. 4 shows theparts when the breaker has been tripped to open position. The mainclosing element of the breaker is the hand lever 22 which is pivoted onthe pin 22a which is supported by the two sides of the frame 2i. Thisclosing element extends forwardly through vertical slots in theinsulating plate I1 and in the front portion of the casing 2 forpermitting upward and downward movement of the hand lever. The rear end22o of the main closing lever extends downwardly from the pin 22a and ispivotally connected to a pair of links 23 forming a toggle therewith.The links 23 are pivotally connected to a pair of links 24 which in turnare pivotally connected by a pin 24a to an arm 25 which embraces theinsulation 5 on the contact shaft 4 and is clamped thereto. The ends ofthe pins 24a project into circular slots Zic in the sides of the frame 2I. The upper ends of these slots serve as stops to limit the openposition of the breaker. The links 24 and arm 25 serve to transmit theclosing force from the handle 22 and the closing toggle to the shaft 4and thereby move the contact arms 6 from their open position to theirclosed position by a downward movement of the handle 22. The pin 26which pivotally connects the links 23 and 24 is supported and guided bythe upper ends of a pair of guide links 2l which extend forwardly anddownwardly, as shown in Fig. 5. Their lower ends are pivotally connectedby a pin 28 to a pair of links 29, the inner ends of which are pivn otedon a xed pivot pin 3G which is supported by the two sides of the frame2i. The pin 28 is normally restrained in xed position by a latch 3l, thelower end of which is xed to the trip shaft le. This shaft extendsacross the front of the breaker near the base, as shown in Figs. 1 and 2and is journaled at its ends in the metal plates S. It is likewisejournaled in the lower ends 2lb of the mechanism frame as shown in 5.Between its end journals and the part where it is journaled in themechanism frame, this shaft is square in section, as shown in Fig. 2,and enveloped by a covering Ido of insulating material. Considering theparts in the positions shown in Fig. 5 with the pin 23 restrained by thelatch, it is evident that when the closing arm 22 is depressed, it willtend to straighten the toggle 22h, 23 and force the pin 25 downwardlywhich in turn will force the links 24 downwardly and rotate the arm 25in a clockwise direction and thereby move the shaft 4 and contact arms 6to the closed position shown in Fig. 2. During this closing movement thepin 23 is guided by the links 21 in the arc of a circle about the pin 28as a center. During this movement and also when the breaker is closed,the guide links 21 are under tension and endeavor to pull the pin 28upwardly about the pivot 33 as a center; but cannot do this because thepin 28 is restrained by the latch. in the closed position of the parts,as shown in Fig. 3, the toggle 22o, 23 is overset and the closing handlewill then remain in its lowest position.

When the latch 3| is moved outwardly to release the pin 23, the latteris thrown upwardly about the pivot 38 by the pull of the links 21imposed by the pin 23. The contact arm 25 and links 24 then move upwardrapidly from the position shown in Fig. 3 to the position shown in Fig.4 whereby the contact arms 6 are rapidly moved to their open position.This rapid movement is due not only to the pressure of the contactstending to move the arms 6 outwardly but is also due to the pull of apair of springs 32 which are connected between a lower extension of theclamp of the arm 25 and projections 32a from the support 2 i. Duringthis opening movement of the parts, the closing arm 22 remains in itslowest position, as shown in Fig. 4, the linkage connections permittingopening of the contact arms 6 without ailecting the movement of theclosing element.

The breaker cannot be reclosed without first raising the handle 22 toits upper position. The raising of the handle swings the linkage to theposition in Fig. at which time the Din 28 is engaged by the latch 3| andthe mechanism is then in condition to reclose the breaker by a downwardmovement of the main closing element 22 in the manner already described.The open or closed position of the breaker is shown by a circularindicating plate 33 carried on the periphery of a plate 33a pivoted on apin 33D which is supported by one side of the frame 2|. Pivotallyconnected to the disk 33a above its pivot is a link 34 which ispivotally connected at its rear end to a pin extending from the side ofa clamp which holds the arm in position on the contact shaft. Openingsthrough the casing 2 and insulating plate |1 permit an upper or lowerportion of the indicating plate 33 to be exposed and visible from theoutside of the breaker. When the breaker is open the lower part of theplate 33 is exposed and will show off or other designation through theopening; and when the breaker is closed it is evident that the indicatorwill be moved to expose its upper portion which may be marked on orotherwise designated to indicate a closed condition of the breaker.

The latch 3| is normally biased to engage the pin 23 by a spring 35which is secured at one end to the pin and at its other end to a stripof meta-l 33 which is riveted or otherwise secured to the lower portionof the latch 3|. This latch is adapted to be tripped automatically bythe overload magnet in a manner to be described later but it is alsoadapted to be tripped by the movement of the closing element 22 in adirection that would tend to open the breaker. For this purpose a leverhaving a downwardly extending arm 31 and a rearwardly extending arm 33is pivoted to one side of the frame 2| at the elbow of the lever. Aspring 39 is fixed at one end to a pin 40 which extends between the twosides of the frame 2| and serves as a stop for the closing arm 22 in itslowest position. The lower end of the spring 39 is secured to the arm 38and tends to move this arm upwardly about its pivot. It also tends tomove the arm 31 toward and against the pin 33. The upper end of themetal strip 36 is provided with a sidewise end projection 36a as shownin Fig. l, which is in the path of the lower end of the arm 31v When thelower end of this arm is moved toward the front of the breaker againstthe pressure oi the spring 31 it engages the projection 36a and forcesthe latch outwardly to release the pin 28. This action is accomplishedby a tumbler element 4| which is pivotally mounted on an extension ofthe pin which connects the arm 22h with the links 23. The tumbler 4| isprovided with a downward extension carrying a side pin 4|a which ispositioned above and in the plane of the arm 38. The tumbler is alsoprovided with two upwardly extending tongues Mb and 4|c which are spacedapart 'from each other. A pin 42 extends outwardly from the side of thearm 22D and is positioned between the two tongues of the tumbler and isadapted to be engaged by one or the other of these tongues. A spring 43encircles the pin of the tumbler and has one end extended to engage theside of pin Ma of the tumbler and the other end extended to engage thefront side of the pin 42. This spring consequently tends to keep thetongue 4|c of the tumbler in engagement with the pin 42, as shown inFigs. 3, 4 and 5.

In the upper position of the closing element 22 shown in Fig. 5, the pin4|@ is out of engagement with the upper edge of the arm 33; and in thelowest position of the closing element 22 the pin dla is out ofengagement with the arm 33, as shown in Figs. 3 and 4. The spring 39,under these conditions, causes the rear edge of the arm 31 to engage asleeve on the pin 30 which serves as a stop for the arm. When thebreaker is to be closed by a downward movement of the closing element 32from the position shown in Fig. 5, the pin 4|a will be brought intoengagement with the upper edge of the arm 38 and will follow the contourof this upper edge during the closing movement. This action would tendto depress the arm 33 and cause the lower end of the arm 31 to pushagainst the side projection 36a of the strip 36 and release the latchfrom the pin 28 except for the fact that the tumbler spring 43 issufficiently weak to permit the tumbler to rotate in a clockwisedirection on its pivot and cause the tongue 4|b to approach the pin 42.This yieldability of the tumbler in the closing movement of the breakerthus avoids the depressing of the arm 38 and avoids releasing the latch3|. When, however, the closing element 22 is moved upwardly from theposition shown in Fig. 3 to open the breaker manually, the pin 4|@ isbrought into engagement with the inner upper end of the arm 38 and owingto the fact that the tumbler cannot move in a counter-clockwisedirection by reason of the tongue 4|c engaging the pin 42, the lower endof the tumbler will force the arm 3S downwardly and cause the arm 31 toforce the strip 36 and latch 3| outwardly to release the pin 28. Ittherefore results that the breaker is quickly opened by the release ofthe latch upon the initial movement of the closing element 22 in areverse direction to open the breaker. This prevents the breaker frombeing opened by a, slow separation of the contacts when the breaker isopened manually. Similarly during the closing movement of the breakerfrom the position shown in Fig. 5, on any reverse movement of theclosing element 32, the tumbler will be caused to rotate on its pivot ina counter-clockwise direction and bring the tongue lo against the p-in42. This action then results in the arm 38 being depressed and the latchl released permitting the parts be quickly thrown to open position bythe pull of the springs 32. Thus a reverse movement of the closingelement during any portion of the closing stroke will cause the parts tobe automatically and rapidly thrown to open position which protects thecontacts from the effects of arcing due to a slow separation of thecontacts.

The breaker may be opened automatically upon the occurrence of anyabnormal condition. In the present case an overload coil l I, alreadydescribed, is provided for each pole of the magnet. It is positionedbelow each of the contact arms 6, as shown in Figs. 1 and 2. Theoverload assembly is shown in Figs. 2 and 6. It comprises a U-shapedsupporting frame 44, the base of the U being secured to the panel l andthe arms of the U embracing and supporting an iron or steel frame 45.IThis frame extends forwardly from the rear end of the overload coil andturns upwardly at the iront end of the coil. An iron or steel core 45 isenveloped by an insulating bushing 45a and is located within theoverload coil, being supported at its front end by the upturned end ofthe core 45, as shown in Fig. 6.

The upper portion of this core is slotted to receive a freely movablepush pin 4l. Opposite the end of each of these pins of the threeoverload coils is an arm 48 of sheet metal with outwardly turned edgesand these arms are fixed to the common trip shaft I4, being mounted onthe outside of the insulation |45. When any one of the push pins 41 isforced outwardly, it will engage its arm 48 and turn the trip shaft torelease the latch 3l and thereby cause the automatic opening of thebreaker in the manner already described. An iron or steel armature 49 ofeach overload coil is pivotally mounted on a pin 49a which extendsbetween the two sides of the frame 44. This armature has secured to itsrear side a sheet metal strip 55 which extends around the lower end oithe armature to a point below the end of the armature 49 and then isbent at right-angles and extends downwardly. A spring 5l is secured tothe lower end of the strip 50 and is also secured to a projection 44awhich is an extension from one side of the frame 44. It is evident thatthis spring tends to hold the armature 49 away from the core 46 of theoverload magnet.

A thermostatic control is incorporated with the magnet for the purposeof tripping the circuit breaker after a time interval, depending uponthe duration and amount of the overload current. This is in the form ofa bi-metallic strip 52 which is secured to the front face of the frame45 and extends downwardly and then along the underside of the magneticframe 45 and between this frame and the corner of the metal strip 50.The end of the bi-metallic strip 52 thus serves to adjust the armature49 and acts as a stop for the armature in its unattracted position. Thepositioning of the thermostatic strip 52 close to the magnetic framecauses its temperature to change and approximately correspond with theheating of the overload coil as ras.

determined by the value of the current passing through the circuitbreaker. Under normal loads, or less than normal loads, the rise intemperature of the overload magnet is not suflicient to affectmaterially the thermostatic strip; but upon the occurrence of moderateoverloads, the heating of the overload coil and the magnet frame istransferred to the thermostatic strip, and owing to its being composedof two metal strips having different coeflicients of expansion, causesthe inner end of the bi-metallic strip to move downwardly to an amountdepending upon the temperature rise. This action turns the armature 49on its pivot to a greater or lesser extent against `the action of thespring 5| and moves the armature correspondingly closer to the core Thecloser the armature is brought to the core, the lower the value of thecurrent in the overload coil Il which will attract the armature.

Assuming the circuit breaker to be closed, the automatic opening may beeffected instantaneously upon the occurrence of an excessive overloadbecause the current in the overload winding Il will then be so high thatthe armature 49 will be instantly attracted even though the armature 49is in its outermost position from the core 45. This will drive the pin41 against the arm 48 of the trip shaft and release the latch 3| andthereby cause the automatic opening of the breaker. Upon the occurrenceof a moderate overload the rst effect is to cause the heating of themagnet which results in the thermostatic strip gradually adjusting thearmature 49 closer to its core until a position is reached where thevalue of the overload current is surcient to suddenly attract thearmature and shift the push pin 41 to trip the latch. It is apparentthat the time of response of the breaker to an overload current dependsupon the value of the overload current and the time interval of itscontinuance. It will also be appreciated that by providing an overloadcoil for each pole, the breaker will be tripped and all three sets ofcontacts opened upon the occurrence of an overload current in any one ofthe circuits which is sufficient in value and duration to cause therelease of the latch.

Fig. 7 shows a modiiied form where an expansible thermostatic element isprovided instead of a bi-metallic strip. Here the magnet frame 45a isextended to embrace both ends of the coil Il. A short iron or steel core53 is xed to one end of the frame and extends a short distance withinthe coil Il. A movable magnetic core 54 passes freely through the frameat the other end of the coil. It carries a brass pin 54a which passesfreely through the core 53 and is adapted to engage the arm 48 and tripthe breaker when the plunger core 54 is attracted within the coil Il. Asealed expansible bellows 55 is secured at one end to the outer end ofthe plunger 54. The other end of the bellows carries a flange 55a.Between this flange and the end of the magnet frame and encircling thebellows is a spring 55 which tends to hold the plunger and bellows intheir outer position, the end of the bellows seating against an upwardextension of the frame 44. Within the sealed bellows is a liquid havinga high coefficient of expansion, or a volatile liquid, which causes thebellows to expand longitudinally with increase in temperature. Thisbellows, like the thermostatic strip 52 is in juxtaposition to themagnet so that the heating thereof will correspondingly heat thebellows.

Upon the occurrence of an excessive overload,

the plunger 54 will be attracted within the coil l I instantly againstthe pressure of the spring 5B and cause the immediate tripping of thebreaker. Upon the occurrence of moderate overloads, the magnet andbellows will be heated gradually and cause the gradual expansion of thebellows. This moves the plunger closer to the core 53 until a positionis reached where the overload current will suddenly attract the plungerand trip the breaker. The time delay before this action occurs dependsupon the amount and duration cr the overload. Under normal loads theheating is not suflicient to affect the position of the plungermaterially and under such conditions the breaker is not tripped.

It will be understood that various modifications inay be made to fulfillparticular requirements and to suit the preference of the designerwithout departing from the scope of the invention. The breaker may beprovided with one,

two or more poles and adapted to be tripped by `a shunt tripping coil,under voltage control, auxiliary switch control, as well as the overloadccntrol. Instead of being hand operated, the 'breaker may be arranged tooperate electrically :and may be arranged for front or rear switch-.board mounting. The foregoing description and .accompanying drawingsillustrate a preferred ernlbodiment of the invention.

I claim:

l. In an automatic electric circuit breaker 'having a plurality of poleswith relatively mov- :able contacts and having a common shaft for:actuating the movable contacts, a rear insulating supporting panel, andan insulating partition fextending forwardly from said panel between thepoles and their contacts, said 'partition being formed in sections, oneof said sections being :secured to said panel and partly encircling theshaft on one side thereof and the other of said sections being securedto said panel and partly encircling the shaft on the other side thereof.

2. In an automatic electric circuit breaker having a plurality of poleswith relatively movable contacts and having a common shaft for actuatingthe movable contacts, a rear insulating supporting panel, an insulatingpartition extending forwardly from said panel between the poles andtheir contacts, said partition being formed ing disks carried by theshaft and positioned opposite the portions of said sections where theyencircle the shaft.

3. In an automatic electric circuit breaker having a plurality of poleswith relatively movable contacts and having a common shaft for actuatingthe movable contacts, a rear insulating supporting panel, and aninsulating partition extending forwardly from said panel between thepoles and their contacts, said partition being formed in sections, oneof said sections beiner secured to a lower portion of said panel andpartly encircling the shaft on one side thereof and the other of saidsections being secured to an upper portion of said panel and partlyencircling the shaft on the other side thereof.

4. In an automatic electric circuit breaker having a plurality of poleswith relatively movable contacts and having a common shaft for actuatingthe movable contacts, a rear insulating supporting panel, an insulatingpartition extending forwardly from said panel between the poles andtheir contacts, said partition being formed in sections, one cf saidsections being secured to a lower portion of said panel and partlyencircling the shaft on one side thereof and the other of said sectionsbeing secured to an upper porin sections, one of said sections beingsecured ffii to said panel and partly encircling the shaft on one sidethereof and the other of said sections being secured to said panel andpartly encircling the shaft on the other side thereof, and insulattionof said panel and partly encircling the shaft on the other side thereof,an insulating cover plate secured to the bottom of said first namedsection, and an insulating cover plate secured to the front of saidsecond named section.

5. In an automatic electric circuit breaker having relatively movablecontacts, a rear insulating supporting panel, insulating partitions onopposite sides of said contacts and extending forwardly from said panel,a front insulating plate secured to said partitions and closing thefront space between the partitions, and an are chute positioned betweenthe upper portions of said partitions and removably supported therebyand retained in position by said front plate.

6. In an automatic electric circuit breaker having relatively movablecontacts and having a vertically disposed blow-out coil at one side ofand opposite said contacts, a rear insulating supporting panel,vertically extending insulating partitions on opposite sides of thecontacts, one of said partitions having the blow-out coil enclosedwithin it, and an arc chute positioned between the upper portions ofsaid partitions and supported thereby.

GEORGE A. HEALIS.

